Answer
$P(t)= \frac{ -0.073t^4}{4}+\frac{1.422t^3}{3}- \frac{11.34t^2}{2}+9.236t +C$ percentage points; t decades since $1900$
Work Step by Step
$P(t)=-0.073t^3+1.422t^2-11.34t+9.236$
$P(t)=\int( -0.073t^3+1.422t^2-11.34t+9.236)dt$
$P(t)=-0.073\int t^3 dt+1.422\int t^2 dt- 11.34 \int t dt+9.236\int dt$
$P(t)= \frac{ -0.073t^4}{4}+\frac{1.422t^3}{3}- \frac{11.34t^2}{2}+9.236t +C$ percentage points; t decades since 1900